Last winter I kept my router working for a couple of days without mains power using the low-tech approach of a cable from a surplus HH2 power supply, a couple of crocodile clips, and a car battery.

Same battery powered an inverter for the laptop, too. We were sat watching iPlayer while everywhere for miles around was in darkness and under several feet of snow.

While the DC UPS idea has tempted me a few times, the 5-minute break while I lug an old battery in from the garage can be lived with.

I just happen to have a DC UPS sitting unused so it will be ideal for the task, like you say the modem will go for a long time on the battery.

In reply to a post by Going_Digital:

I just happen to have a DC UPS sitting unused so it will be ideal for the task, like you say the modem will go for a long time on the battery.

Not much use if the router and PC are dead though?

In reply to a post by Going_Digital:

I just happen to have a DC UPS sitting unused so it will be ideal for the task, like you say the modem will go for a long time on the battery.

Car battery of about 80Ah, Load of maybe 0.5A, should give about a week before the voltage drops too far. I suspect longer than that was on the cards, as most "12v" rated kit will work happily with a good bit less.

A sealed lead-acid battery of about 7Ah would do, and be a bit more acceptable in the living room.